Microsoft only sells adware. Google is spyware (and crapware). Linux tablets don't even exist.
Apple focuses on compatibility, user experience, performance, hardware, ease of use (yet still useful for power users). Sure it's been dropping the ball a bit in the past few years, but it's still lightyears ahead of any competitor.
Pure monopoly means single supplier, but companies having monopoly power where they have the ability to increasingly behave independently of competitive pressures is more common. https://en.wikipedia.org/wiki/Lerner_index
Apple should be forced to stop these anticompetitive practices.
Your line of thought only works if the developers are the customer- they are not in Apple's case.
Your line of thought is the narrow "Chicago School" thinking Robert Bork in the US in the 90s where the sole focus is on the benefits to consumers and overall efficiency.
One of the reasons why Google Chrome enjoys its monopoly is because Apple does a terrible job with its browser Safari. Terrible. I mean it's a train-wreck! Since iOS 10 or probably little later they have done nothing but destroy how the web apis are supposed to function, abusing every single accessibility guideline into something that is at best a line of defense to promote their app store.
I hesitantly moved away from iPhone X to Android Pixel last month.
Chrome on the other hand... well, it's Google, one of the largest purveyors of advertising. If you don't think Chrome is watching you, I've got a bridge to sell you.
Maybe it’s telling the truth when it says there are security concerns?
If they allow alternate app store or browsers then yes apple is bold. Until then they need to consider their bottomline which requires sometimes bowing to China as well!